 /*******************************************************************************
  * Copyright (c) 2000, 2007 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.handlers;

 import java.util.Map ;

 import org.eclipse.core.commands.AbstractHandler;
 import org.eclipse.core.commands.ExecutionEvent;
 import org.eclipse.core.commands.ExecutionException;
 import org.eclipse.core.runtime.IAdaptable;
 import org.eclipse.jface.window.Window;
 import org.eclipse.ui.IPerspectiveDescriptor;
 import org.eclipse.ui.IWorkbench;
 import org.eclipse.ui.IWorkbenchPage;
 import org.eclipse.ui.IWorkbenchWindow;
 import org.eclipse.ui.PlatformUI;
 import org.eclipse.ui.WorkbenchException;
 import org.eclipse.ui.internal.WorkbenchPlugin;
 import org.eclipse.ui.internal.dialogs.SelectPerspectiveDialog;

 /**
  * Shows the given perspective. If no perspective is specified in the
  * parameters, then this opens the perspective selection dialog.
  *
  * @since 3.1
  */
 public final class ShowPerspectiveHandler extends AbstractHandler {

     /**
      * The name of the parameter providing the perspective identifier.
      */
     private static final String PARAMETER_NAME_VIEW_ID = "org.eclipse.ui.perspectives.showPerspective.perspectiveId"; //$NON-NLS-1$

     public final Object execute(final ExecutionEvent event)
             throws ExecutionException {
         IWorkbenchWindow window = HandlerUtil.getActiveWorkbenchWindowChecked(event);
         
         // Get the view identifier, if any.
 final Map parameters = event.getParameters();
         final Object value = parameters.get(PARAMETER_NAME_VIEW_ID);
         if (value == null) {
             openOther(window);
         } else {
             openPerspective((String ) value, window);
         }

         return null;
     }

     /**
      * Opens a view selection dialog, allowing the user to chose a view.
      *
      * @throws ExecutionException
      * If the perspective could not be opened.
      */
     private final void openOther(final IWorkbenchWindow activeWorkbenchWindow)
             throws ExecutionException {
         final SelectPerspectiveDialog dialog = new SelectPerspectiveDialog(
                 activeWorkbenchWindow.getShell(), WorkbenchPlugin.getDefault()
                         .getPerspectiveRegistry());
         dialog.open();
         if (dialog.getReturnCode() == Window.CANCEL) {
             return;
         }

         final IPerspectiveDescriptor descriptor = dialog.getSelection();
         if (descriptor != null) {
             openPerspective(descriptor.getId(), activeWorkbenchWindow);
         }
     }

     /**
      * Opens the perspective with the given identifier.
      *
      * @param perspectiveId
      * The perspective to open; must not be <code>null</code>
      * @throws ExecutionException
      * If the perspective could not be opened.
      */
     private final void openPerspective(final String perspectiveId,
             final IWorkbenchWindow activeWorkbenchWindow)
             throws ExecutionException {
         final IWorkbench workbench = PlatformUI.getWorkbench();

         IAdaptable input = null;

         final IWorkbenchPage activePage = activeWorkbenchWindow.getActivePage();
         if (activePage != null) {
             input = activePage.getInput();
         }

         try {
             workbench.showPerspective(perspectiveId, activeWorkbenchWindow,
                     input);
         } catch (WorkbenchException e) {
             throw new ExecutionException("Perspective could not be opened.", e); //$NON-NLS-1$
 }
     }
 }

